Generally, belt layers of pneumatic radial tires for passenger cars have the construction in which two belt layers having steel cords aligned obliquely in a tire circumferential direction and having cut ends of the steel cords at both end portions thereof are laminated in such a fashion that the steel cords cross one another between the layers. The belt layers having such a construction involve the problem that because a stress is likely to concentrate on the cut end portions of the steel cords due to a load during driving, so-called "edge separation" or in other words, peel of the steel cord ends from the rubber layer, is likely to occur. The same problem develops also in heavy load pneumatic radial tires for small trucks and for trucks and buses having three or more belt layers.
The belt layers of the conventional pneumatic radial tires have the two-layered structure wherein a belt layer having steel cords inclined to the right in a tire circumferential direction and a belt layer having steel cords inclined to the left are laminated. For this reason, the belt layers having such a two-layered structure inevitably generates a spiral torsion due to the tensile strength in the tire circumferential direction that occurs when the tire rolls. Since this torsion of the belt layers generates a lateral force to the tire, the tire undergoes drift or runs toward one side at the time of straight driving and straight driving stability is impeded.